The present invention, in some embodiments thereof, relates to methods and systems of imaging and, more particularly, but not exclusively, to methods and systems of imaging using optical interferometry. Optical interferometry combines two or more light waves in an optical instrument in such a way that interference occurs between them.
Sub-millimeter diameter endoscopes are being examined for usage in many clinical applications that require minimal tissue damage. The harsh size constraints result with reduction of the number of imaging fibers in fiber bundle endoscopes and limit the frame rate of lateral scanning single optical-fiber probes. Recently, a new method termed spectrally-encoded endoscopy (SEE) was introduced, utilizing a single optical fiber and miniature diffractive optics to encode transverse reflections from a sample, see Tearney, G. J., M. Shishkov, and B. E. Bouma, Spectrally encoded miniature endoscopy. Opt. Lett., 27(6): p. 412-414, 2002 and Yelin, D., et al., Three-dimensional miniature endoscopy. Nature, 443(7113): p. 765-765, 2006, which is incorporated herein by reference. Since rapid lateral scanning is not required, SEE uses slow axis scanning by probe rotation, and is thus capable of high quality imaging through ultra-miniature, single fiber endoscopic probes.
This technique combines optical interferometry, for example in order to extract depth information from the sample. Using low coherence interferometry, allows using a SEE device to capture a three dimensional video imaging of a surface and subsurface tissue structures, as well as Doppler imaging of acoustic vibrations and flow, see Yelin, D., B. E. Bouma, and G. J. Tearney, Volumetric sub-surface imaging using spectrally encoded endoscopy. Optics Express, 16(3): p. 1748-1757, 2008 and 5. Yelin, D., et al., Doppler imaging using spectrally-encoded endoscopy. Optics Express, 16(19): p. 14836-14844, 2008, which are incorporated herein by reference. It should be noted that the imaging depth range of an interferometric SEE system is usually limited by the resolution of the interferometric spectral measurement to a few millimeters.
SEE is usually implemented using a quasi-monochromatic or broad bandwidth light source which illuminates a single optical fiber. At the distal end of the fiber, a diffractive or dispersive optic, such as a single diffraction grating and a single lens, disperses the light across a target object, which is reflected and returns back through the diffractive or dispersive optic and optical fiber. Light from the optical fiber is detected by a wavelength detecting apparatus, such as a spectrometer. By detecting the light intensity as a function of wavelength, the image may be reconstructed. SEE techniques have been described in, for example, U.S. Patent Publication Nos. 2007/0233396 and 2008/0013960.
Conventional endoscopy uses RGB color information as cues to diagnosis. By using wavelength information to encode spatial location, SEE images utilize much of the color information to encode spatial location and therefore important color information may be lost. Accordingly, there may be a need to address and/or overcome at least some of the deficiencies described herein above.